Apparatus, and associated method, for operating upon received data at a receiving station capable of diversity operation

ABSTRACT

Apparatus, and an associated method, for a receiving station, such as the receive part of a mobile station, that has diversity antennas. The receiving station includes both legacy demodulators and a diversity demodulator. Calculations are made to determine signal indicia associated with the signal energy detected at the diversity antennas. Responsive to the signal indicia, selection is made as to whether to utilize demodulation data, demodulated pursuant to a diversity demodulation technique or pursuant to a legacy demodulation technique. As the characteristics of received signals change, reselection of the demodulation is correspondingly made, such as on a frame-by-frame basis of frame-formatted data.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 12/026,105 filed on Feb. 5, 2008, which claims priority toprovisional patent application No. 60/888,167 filed on 5 Feb. 2007, thecontents of which are incorporated herein by reference.

The present invention relates generally to a manner by which tofacilitate operation of a receiver, such as the receive part of acellular mobile station, capable of providing receive diversity throughthe use of a set of receive antennas. More particularly, the presentinvention relates to apparatus, and an associated method, by which toselect in what manner to demodulate received data. Depending upon thecharacteristics of the received data, either diversity demodulation isselected to be used or legacy, i.e., conventional demodulation, isselected to be used. Reselection of the manner of demodulation isfurther provided. If the characteristics of the received data change ina way to cause the preferred manner by which to demodulate the data tochange, then the manner of demodulation is to be changed.

BACKGROUND OF THE INVENTION

A variety of different types of mobile communication systems have beendeveloped and deployed and are regularly utilized for communication.And, for many, ready access to a mobile communication system tocommunicate therethrough is a practical necessity. In a mobile radiocommunication system, as well as other types of communication systems,data is communicated between a set of communication stations including asending station and a receiving station by way of a communicationchannel. In a mobile, or other radio, communication system, thecommunication channel is defined upon a radio link, part of theelectromagnetic spectrum. The communication channel is non-ideal. Duringcommunication of the data upon the communication channel, the signalcontaining the data can become distorted. Additional distortion issometimes also introduced upon the data once received at a receivingstation. If the distortion is significant, the informational content ofthe data cannot accurately be recovered. Various techniques are providedin order to make compensation for, or otherwise to overcome, thedistortion introduced upon the data. Space diversity, for instance, issometimes provided, either at a sending station or at a receivingstation, or both. Space diversity is created at a sending station, forinstance, through the use two or more spaced-apart transmit antennas,thereby to provide spatial redundancy. Analogously, at a receivingstation, use of two or more receive antennas analogously providesspatial diversity. In a cellular, or other mobile radio, communicationsystem in which mobile stations are used by which to communicate,spatial diversity techniques have conventionally been utilized only atthe network part of the communication system.

Use of diversity antennas at a mobile station has been, to date,generally limited. Mobile stations are generally small form-factordevices. Their small physical dimensions limit the use of multipleantennas. Additionally, use of multiple antennas also requires acorresponding increase in RF (Radio Frequency), front-end and base bandprocessing of received data. Increased processor complexity andcomputational ability is required. Such increases result in acorresponding increase in power dissipation, adversely affecting batterylongevity.

However, various advancements in circuit, and other, technologies, haveincreased the feasibility of use of spatial diversity at a mobilestation.

Efforts, therefore, have been directed towards providing spatialdiversity to a mobile station. For instance, work related to DARP(Downlink Advanced Receiver Performance) attempts to utilize an advancedreceiver in a mobile terminal, having a single antenna, to increase thetolerance of the receive part of the mobile terminal to co-channelinterferers. MSRD (Mobile Station Receiver Diversity) requirements areset forth therein for evolved EDGE (Enhanced Data for GSM Evolution) andare based, in part, on the DARP efforts.

Advanced receivers are implementable in various different manners. Forinstance, such receivers variously include, e.g., Joint Space TimeOptimizing Filters (JSTOFs) or Weiner filters, and utilize, e.g., jointdetection (JD) techniques. In DARP-related standardizations, envisionedcommunication signaling pertained primarily to improvements of GMSK(Gaussian Minimum Shift Keying) signaling. For instance, such signalingpertained to GSM (Global System for Mobile Communications) voiceservices, GPRS (General Packet Radio Service) and the most-robustModulation and Coding Schemes (MCS) used in EDGE-based communications atlower data interchange speeds, e.g., MCS-1 through MCS-4. Simpleextension of the capabilities of DARP requirements to more-complextechniques, such as 8-PSK, 16-ary or 32-ary modulation techniques, usedfor higher-speed EDGE modulation and coding schemes, are generallyenvisioned to require, or be improved by the use of multiple RFreceivers, amenable for multiple-antenna implementations.

Various issues remain with respect to use of spatial diversity at asmall form-factor receive station, such as a mobile station. And,further efforts with respect to implementation of such receivingstations that have spatial diversity is required.

It is in light of this background information related to the use ofspatial diversity in communication systems that the significantimprovements of the present invention have evolved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional block diagram of a radio communicationsystem in which an embodiment of the present invention is operable.

FIG. 2 illustrates a functional block diagram, similar to that shown inFIG. 1, but in which a receiving station operates pursuant to analternate embodiment of the present invention.

FIG. 3 illustrates a method flow diagram representative of the method ofoperation of an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention, accordingly, advantageously provides apparatus,and an associated method, for a receiver, such as the receive part of amobile station, that is capable of providing receive diversity throughuse of a set of spaced-apart, receive antennas.

Through operation of an embodiment of the present invention, a manner isprovided by which to select in what manner to demodulate received data.

In one aspect of the present invention, depending upon thecharacteristics of the received data, either diversity demodulation isselected to be used or legacy, i.e., conventional, single-chaindemodulation is selected to be used.

In another aspect of the present invention, reselection of the manner ofdemodulation is further provided. If the characteristics of the receiveddata change in a way such that a different demodulation-type wouldbetter facilitate recovery of the informational content of the data, achange of the manner by which the received data is demodulated is made.

In another aspect of the present invention, a multiple-antennaarrangement is provided for a small form-factor mobile station. Throughthe use of separate antennas the strength of the signal energy of thecommunicated data that is detected at the respective antennas, andapplied to receiver front-ends, might well differ. In addition, thesignals received at the respective antennas and applied to the receiverfront-ends may exhibit some correlation. Various factors affect thesignal correlation and signal strength. The multi-path fadingenvironment of the radio channel, the design of the antennas, theirphysical separation, and the construction, and configuration, of themobile station are all exemplary affecting factors. Additionally,signal-strength-affecting factors include, e.g., channel fadingconditions and even the position of a user as the user operates themobile station. In addition, the frequency band of operation is anexemplary factor that affects signal strength and the correlationbetween two or more signal paths received by two or more separatereceivers.

In another aspect of the present invention, a receiver structure isprovided that includes a diversity demodulator that is connected toreceive indications of signal energy detected at the separate antennasof the diversity-antenna arrangement. When the detected signal energy isof characteristics such that diversity demodulation would be thebeneficial manner by which to demodulate the detected data, results ofthe diversity demodulation are used in the receive chain to recover theinformational content of the detected data.

In another aspect of the present invention, the receiver structurefurther includes legacy, i.e., conventional, demodulators configured inseparate receive-chain paths with the separate ones of the antennas ofthe set of diversity antennas. The legacy demodulators demodulate signaldata of the single antennas to which the respective demodulators arecoupled. Depending upon the characteristics of the receive signals,legacy-demodulated data, demodulated by a selected legacy demodulator,is used with additional receive chain elements to recover theinformational content of the communicated data.

In another aspect of the present invention, signal indicia measurementis made of the detected data, such as to determine a quality metricassociated with the detected data, correlation between signal energydetected at the separate ones of the antennas, amplitude differencesthere between, as well as any of various other measurements and indicia.Evaluation is made of the calculated or measured indicia, anddetermination is made as to which demodulated data, one of thelegacy-demodulated data or the diversity-demodulated data, is to be usedto recover the informational content of the received signal. Successiveiterations of the measurements or calculations are made. If theconditions change to an extent that the manner by which the modulationis to be performed changes, a change is made. When, for instance, thecommunicated data comprises frame-formatted data, new measurements andcalculations are made on a frame-by-frame basis, or intermittently,e.g., every selected number of frames. And, new selection of whether toutilize diversity demodulated data or legacy-demodulated data is made.Thereby, as characteristics of the communicated data change, demodulateddata that best facilitates recovery of the informational content of thedetected data is made.

In another aspect of the present invention, indicia measurement,calculation, evaluation, and selection is made prior to demodulation ofthe data. And, responsive to the selection, the appropriate demodulatoris made operable to demodulate the detected data. Alternately, all ofthe demodulators are concurrently operable, and selection is made as towhich of the demodulated data is to be provided to additional receivechain elements for further processing.

Thereby, receive diversity is provided to a receiving station whileproviding for demodulation of the detected data in a manner that bestfacilitates recovery of its informational content.

In these and other aspects, apparatus, and an associated method, isprovided for a receiving station that contains a first diversity antennaand a second diversity antenna. A receive signal indicia operator isadapted to receive a first signal indicia associated with first signalenergy detected at the first diversity antenna and to receive a secondsignal indicia associated with second signal energy detected at thesecond diversity antenna. The receive signal indicia operator isconfigured to operate upon the first and second signal indicia,respectively, to ascertain an attribute thereof. A selector is adaptedto receive an indication of the attribute ascertained by the receivesignal indicia operator. The selector is configured to select which ofdiversity demodulation results of a combination of the first and secondsignal energy, and separate demodulation results of the first signalenergy or the second signal energy, are to be used at the receivingstation.

Referring first, therefore, to FIG. 1, a radio communication system,shown generally at 10, provides for radio communications with mobilestations, of which the mobile station 12 is representative. The receivepart of the mobile station 12 is represented in FIG. 1. The mobilestation communicates with a radio access network (RAN) 14 that includesa plurality of base transceivers 16 here, e.g., BTS, NODEBs or eNODES.Here, the mobile station is positioned at a location permitting itsreception of signals sent by a desired base station 16-1 and, additionalbase stations 16-2 whose signals that are sent on channels thatinterfere with the signals sent by the base station 16-1.

In the exemplary implementation, the communication system 10 forms acellular radio communication system operable in general conformity withthe operating procedures and protocols a GSM/GPRS/EDGE (Global Systemfor Mobile communications/General Packet Radio Service/Enhanced Data forGSM Evolution)—capable cellular communication system. More generally,the communication system is representative of any of various types ofcommunication systems that benefit from the use of diversitycommunication techniques. And, while downlink communications aredescribed, more generally, the communications are representative ofcommunications between any set of communication stations formed of asending station and a receiving station.

The radio channels are multi-path channels and signals sent by both thebase station 16-1 and the interfering base stations 16-2 arecommunicated upon multi-paths, here shown by paths 18-1 and 18-2.Multi-path communication results in fading conditions, both with respectto the desired signal and with respect to the co-channel, interferingsignals.

The receive part of the mobile station that includes, here, a pair ofreceive antennas 22-1 and 22-2, positioned, such as by beingspaced-apart from one another by appropriate, effective separationdistances, to provide receive antenna diversity. Spatial diversity canbe provided in other manners, too, e.g., by use of directional antennas.The antennas 22 operate in conventional manner to transduceelectromagnetic energy into electrical energy that is representative ofthe detected signal energy. The detected signal energy includes both thedesired signal and interference, both co-channel interference andinterference caused by multi-path transmission. The signal energy andphases detected at the antennas are correlated. The correlation ismodeled as a complex correlation and is designated as “rho”. Correlationis modeled, e.g., in complex terms. The instantaneous value of thecorrelation is a function of the radio propagation environment, theantenna design, and the physical layout of the mobile terminal device.

Electrical indications representative of the detected signal energy atthe antennas 22 are provided on lines 24-1 and 24-2. The indications areoperated upon by conventional gain, and other, elements 26 and 28, inconventional manner to provide amplified indications to RF (RadioFrequency) elements 32. In addition to gain elements traditionallypresent, the gain elements illustrated here by factors G1 and G2 alsoinclude variable attenuation factors. These variable factors can includebut are not limited to attenuation due to the mobile station userpositioning, and can also account for noise-figure differences in theseparate receive chains. The configuration of these elements providesfor different signals detected at the separate antennas. The signals arecorrelated using weighting factors at the elements 26. An amplifiedindication of the electrical representation of the detected signalenergy, detected at the antenna 22-1 is provided to the RF element 32-1.And, an amplified indication of the electrical representation of thedetected signal energy, detected at the antenna 22-2, is provided to theRF element 32-2. RF operations are performed at the respective elements32-1 and 32-2.

The receive part of the mobile station includes apparatus 36 of anembodiment of the present invention. The apparatus 36 is formed offunctional elements, implementable in any desired manner, including, inpart, by algorithms executable by processing circuitry. The apparatusforms demodulated, baseband data on the line 38 that is provided toadditional receive-part elements (not shown), conventionally utilized torecover the informational content of data, such as data communicatedpursuant to a GSM/GPRS/EDGE communication service.

The apparatus includes legacy, i.e., conventional, demodulators 42. Thelegacy demodulator 42-1 is coupled to the RF element 32-1 and receivesan indication that is representative of the signal energy detected atthe antenna 22-1. Analogously, the legacy demodulator 42-2 is coupled tothe RF element 32-2 and receives an indication of the signal energydetected by the antenna 22-2. The legacy demodulators demodulate, inconventional manner, the indications provided thereto. The demodulators42-1 and 42-2 operate independently in that the indications applied tothe respective demodulators 42 are representative of the signal energydetected at the separate antennas.

The apparatus 36 further includes a diversity demodulator 44. Thediversity demodulator is coupled to both of the RF elements 32-1 and32-2. The diversity demodulator demodulates, according to a diversitydemodulation technique, a combination of the indications of the signalenergy detected at both of the antennas 22-1 and 22-2.

Depending upon the characteristics of the signal energy detected at theantennas, one type of demodulation may provide a better error rate thanthe others. That is to say, the legacy demodulation is preferable to thediversity demodulation when the receive signal energy in each of thebranches is of first characteristics. And, diversity demodulation ispreferable to the legacy demodulation when the receive signal energy ineach of the branches is of second characteristics. Lines 46-1 and 46-2extend from the respective legacy demodulators to a quality metriccalculator 48. And, line 52 extends from the diversity demodulator 44 tothe quality metric calculator. The quality metric calculator operates tocalculate selected quality metrics associated with the demodulated data,demodulated by the demodulators 42 and 44. Exemplary quality metricscalculated by the calculator include a BER (Bit Error Rate), a BLER(Block Error Rate), an FER (Frame Error Rate), an SNR (Signal-to-Noise)ratio, a C/I (Carrier to Interference Ratio), a SINR(Signal-to-Interference plus Noise ratio), an associated E_(b)/N₀, orany other appropriate metric.

Calculated values formed by the calculator 48 are provided, hererepresented by way of the lines 56, to a signal quality evaluationmodule and selector 58. The element 58 makes selection, responsive tothe quality metric value or values provided thereto of which of thedemodulated data is to be formed on the line 38 and used pursuant tofurther receive chain operation. In one implementation, the evaluationmodule and selector 58 employs a searching algorithm that operates,e.g., to perform a mathematical MIN operation that determines amathematical minimization of a sum or a weighted sum of all error ratemetrics. In another implementation, the evaluation module and selector58 operates to perform a mathematical MAX operation that determines amathematical maximization of a sum or a weighted sum of all signalquality metrics. Responsive to such calculations, a decision is made asto which demodulated data stream is to be forwarded on the line 38.

FIG. 2 again illustrates the communication system 10. The communicationsystem 10 again is shown to include a mobile station 12, a radio accessnetwork 14 having a plurality of base transceiver stations 16, andmulti-paths 18 upon which signals generated at the base transceiverstations are communicated to the mobile station.

The receive part of the mobile station is again shown to include a setof receive antennas 22, which transduce electromagnetic energy intoelectrical energy on the lines 24. Circuit elements 26 and 28 and RFelements 32 are again shown at the RF part of the receive chain of themobile station. And, the line 38 extends to additional receive chainelements (not shown). Here, the apparatus 36 operates pursuant to analternate embodiment of the present invention. Again, the apparatus 36includes legacy demodulators 42-1 and 42-2 and a diversity demodulator44, each coupled in the same manners to the RF elements 32, eitherseparately with respect to the legacy demodulators or to both of theelements with respect to the diversity demodulator. In thisimplementation, the legacy demodulators 42 are connected by way of thelines 66-1 and 66-2, respectively, to a first side of a switch element68. And, a line 72 extends from the demodulator 44 to the first side ofthe switch element 68. A second side of the switch element 68 isconnected to the line 38.

In this implementation, the apparatus also includes a correlationdetector 74 and an amplitude difference calculator 76. The functions 74and 76 are coupled to the RF elements 32 to receive indications of thesignal energy detected at the respective antennas 22. The correlationdetector 74 operates to calculate the correlation between the signalenergy and phase received at the input to the apparatus 36 s. And, theamplitude difference calculator operates to calculate differencesbetween the amplitudes of the signal energy.

Calculations made by the functions 74 and 76 are provided to ademodulation selector 78. Responsive to the values provided thereto,selection is made by the selector as to which of the demodulation types,i.e., legacy demodulation or diversity demodulation, is to be utilizedto demodulate values on the line 38. And, responsive to the selection,the selected demodulation operation is performed only by the appropriatedemodulator, 42 or 44.

In the embodiment shown in FIG. 2, the demodulation decision is madeprior to the demodulation rather than subsequent to demodulation, asutilized in the embodiment shown in FIG. 1.

Determination is made at the elements 58 and 78 in FIGS. 1 and 2,respectively, to cause demodulated data to be formed on the line 38formed alternately by a legacy demodulation technique or by a diversitydemodulation technique. The selection is made of the demodulationtechnique that yields a best signal quality of the baseband data, e.g.,subject to constraints. The constraints include, for instance, theconstraint that both of the receive chain parts be available fordiversity reception, that is, the second receive chain is not being usedto receive additional information on a different receive frequency, andneither receive chain part is powered-down, such as might occur toreduce current consumption at the mobile station. An additionalconstraint is, e.g., that the mobile station has the processing capacityto demodulate the data individually at both of the receive chains aswell as jointly by the diversity demodulator during each successiveframe of the receive data. An additional constraint is, e.g., that thesignal quality metric calculations performed on the receive data isupdated during each frame. The quality metric values, in oneimplementation, are further averaged or filtered using different FIR orIIR filter techniques over a time period, such as the duration of a callor packet transfer.

In the embodiment shown in FIG. 1, the signals formed on the separate RFchains are demodulated individually with legacy demodulators as well asjointly with the diversity demodulator. Various quality metrics, such asthose previously mentioned, are used to determine selection of whichstream of demodulated data is to be formed on the line 38 and provided,e.g., to baseband processing elements.

In the embodiment shown in FIG. 2, the signals formed on the separate RFchains are provided to the amplitude difference calculator 76 and to thecorrelation detector 74. Calculations performed thereat are provided tothe selector 78. And, selection is made of the demodulation-type to beutilized responsive to such values. The selector, in one implementation,first analyzes the amplitude difference calculated by the amplitudedifference calculator. If the amplitude difference between the signalson the separate paths is greater than a selected threshold, theselection chooses legacy demodulation using the legacy demodulatorconnected to the signal path on which the signal energy of the greatestamplitude to be utilized and to form the demodulated data generated onthe line 38. The selected threshold is, e.g., based upon the diversityreceiver implementation and system simulations and is set, e.g., to alevel at which the diversity receiver no longer performs as well as alegacy demodulator.

In an alternate embodiment, further determination is made whether thesignal energy amplitude generated on the separate RF paths is above aselected level, a “good signal threshold” level but in which theamplitude level difference is greater than the selected level. If thedemodulator is capable of calculating the interference level, then theselector selects the demodulator on the receive path that exhibits thegreater SINR level.

If the amplitude difference determined by the calculator 76 is less thanthe selected threshold, then calculations made by the correlationdetector are examined. If the calculated correlation is greater than aselected threshold, then legacy demodulation is utilized. The legacydemodulator connected in the receive chain that has the greatest powerlevel is used. In an alternate implementation, in an occurrence in whichthe amplitude level difference is acceptable but the correlation betweenthe signals on the respective receive chain branches is greater than aselected threshold, the selector operates to perform demodulation at thelegacy demodulator in the branch that exhibits the greater SINR levelwhile also having an energy amplitude level above the selected “goodsignal threshold”. In another implementation of this occurrence, the twolegacy demodulators perform certain initial processing (e.g. channelestimation and matched filtering) and then combine them to improve SNR.The combined signal is used for the rest of the demodulation.

If, conversely, the detected correlation is less than the selectedthreshold, and the amplitude difference is also less than a selectedthreshold, then diversity demodulation is selected to be utilized. InFIG. 2, the selector 78 generates a signal on the line 82 that causesoperation of the demodulators 42 and 44. And, the selector furthergenerates a signal on the line 84 that controls positioning of theswitch element 68 in a correspondingly appropriate manner.

That is to say, responsive to selection by the selector, an appropriateone of the legacy demodulator 42-1 or 42-2, or the diversity demodulator44, is selected. And, the switch element 68 is caused to be positionedto pass the demodulated data on to the line 38 for further processing.

FIG. 3 illustrates a method flow diagram, shown generally at 102,representative of the method of operation of an embodiment of thepresent invention. The method operates to facilitate data recovery at areceiving station that has a first diversity antenna and a seconddiversity antenna.

First, and as indicated by the block 104, a first and a second signalindicia are obtained. The first signal indicia is associated with firstsignal energy detected at the first diversity antenna. And, a secondsignal indicia associated with signal energy detected at the seconddiversity antenna is obtained.

Then, and as indicated by the block 106, an attribute associated withthe first and second signal energy is ascertained. Then, and asindicated by the block 108, selection is made, responsive to theascertained attribute, to which of diversity demodulation results of thecombination of the first and second signal energy and separatedemodulation results of the first signal energy or the second signalenergy is to be used at the receiving station.

Thereby, a manner is provided by which to utilize demodulated datadepending upon the characteristics of the detected signal energy. Ascharacteristics of the detected signal energy change, reselection of thedemodulation is correspondingly made and the demodulation-type ischanged, if needed. Improved receiver performance thereby results.

1. Apparatus for a radio receiver employing a first diversity antennathat develops a first electrical energy signal from an electromagneticsignal comprising data modulated thereon and a second diversity antennathat develops a second electrical energy signal from the electromagneticsignal, comprising: a first legacy demodulator coupled to the firstdiversity antenna; a second legacy demodulator coupled to the seconddiversity antenna; a diversity demodulator coupled to both the firstdiversity antenna and the second diversity antenna; an amplitudedifference calculator coupled to both the first diversity antenna andthe second diversity antenna; a correlation detector coupled to both thefirst diversity antenna and the second diversity antenna; and ademodulator selector accepting a representation of an amplitudedifference between the first electrical energy signal and the secondelectrical energy signal from said amplitude difference calculator anddetermining whether said representation of an amplitude difference isless than an amplitude threshold, accepting a representation ofcorrelation between the first electrical energy signal and the secondelectrical energy signal from said correlation detector when saidrepresentation of an amplitude difference is less than said amplitudethreshold and determining whether said representation of correlation isless than a correlation threshold, and selecting said diversitydemodulator to demodulate the modulated data when said representation ofcorrelation is less than said correlation threshold.
 2. The apparatus ofclaim 1 wherein said representation of an amplitude difference is notless than said amplitude threshold and wherein said demodulator selectorresponsively selects one of said first legacy demodulator and saidsecond legacy demodulator to demodulate the modulated data.
 3. Theapparatus of claim 2 wherein said first legacy demodulator and saidsecond legacy demodulator further comprise at least one interferencelevel calculator, whereby a determination of signal-to-interferenceratio is made, said demodulator selector responsively selects one ofsaid first legacy demodulator and said second legacy demodulator todemodulate the modulated data based on which of said first legacydemodulator and said second legacy demodulator exhibits the greatersignal-to-interference ratio.
 4. The apparatus of claim 2 furthercomprising a reselector, responsive to demodulated data, that causessaid demodulator selector to operate to reselect one of said firstlegacy demodulator, said second legacy demodulator, and said diversitydemodulator when a characteristic of said demodulated data changes. 5.The apparatus of claim 2 further comprising a switch coupled to saiddemodulator selector that switches between one of said first legacydemodulator, said second legacy demodulator, and said diversitydemodulator.
 6. The apparatus of claim 1 wherein said representation ofcorrelation is not less than said correlation threshold and wherein saiddemodulator selector responsively selects at least one of said firstlegacy demodulator and said second legacy demodulator to demodulate themodulated data.
 7. The apparatus of claim 6 wherein said first legacydemodulator and said second legacy demodulator further comprise at leastone interference level calculator, whereby a determination ofsignal-to-interference ratio is made, said demodulator selectorresponsively selects one of said first legacy demodulator and saidsecond legacy demodulator to demodulate the modulated data based onwhich of said first legacy demodulator and said second legacydemodulator exhibits the greater signal-to-interference ratio.
 8. Theapparatus of claim 6 wherein said first legacy demodulator and saidsecond legacy demodulator each further comprise an initial signalprocessor and wherein said demodulator selector further comprises acombiner coupled to said first legacy demodulator initial signalprocessor and said second legacy demodulator initial signal processor.9. The apparatus of claim 8 wherein each said initial signal processorfurther comprises a channel estimator and a matched filter.
 10. Theapparatus of claim 1 further comprising an energy amplitude determinerthat determines when the first electrical energy and the secondelectrical energy are greater than a signal threshold.
 11. A method foroperating a radio receiver employing a first diversity antenna thatdevelops a first electrical energy signal from an electromagnetic signalcomprising data modulated thereon and a second diversity antenna thatdevelops a second electrical energy signal from the electromagneticsignal, comprising: calculating a representation of an amplitudedifference between the first electrical energy signal and the secondelectrical energy signal; detecting a correlation value for the firstelectrical energy signal and the second electrical energy signal;determining whether said representation of an amplitude difference isless than an amplitude threshold; determining whether said correlationvalue is less than a correlation threshold when said representation ofamplitude difference is less than said amplitude threshold; andselecting a diversity demodulator to demodulate the modulated data whensaid correlation value is less than said correlation threshold.
 12. Themethod of claim 11 further comprising selecting one of a first legacydemodulator and a second legacy demodulator to demodulate the modulateddata when said representation of an amplitude difference is not lessthan said amplitude threshold.
 13. The method of claim 12 wherein saidfirst legacy demodulator and said second legacy demodulator furthercomprise at least one interference level calculator, further comprisingdetermining a signal-to-interference ratio and responsively selectingone of said first legacy demodulator and said second legacy demodulatorto demodulate the modulated data based on which of said first legacydemodulator and said second legacy demodulator exhibits a greatersignal-to-interference ratio.
 14. The method of claim 12 furthercomprising reselecting one of said first legacy demodulator, said secondlegacy demodulator, and said diversity demodulator when a characteristicof said demodulated data changes.
 15. The method of claim 11 furthercomprising selecting one of a first legacy demodulator and a secondlegacy demodulator to demodulate the modulated data when saidcorrelation value is not less than said correlation threshold.
 16. Themethod of claim 13 wherein said first legacy demodulator and said secondlegacy demodulator further comprise at least one interference levelcalculator, further comprising determining a signal-to-interferenceratio and responsively selecting one of said first legacy demodulatorand said second legacy demodulator to demodulate the modulated databased on which of said first legacy demodulator and said second legacydemodulator exhibits a greater signal-to-interference ratio.
 17. Themethod of claim 15 further comprising combining an output of said firstlegacy demodulator and an output of said second legacy demodulator. 18.The method of claim 17 wherein said combining further comprises achannel estimation and matched filtering of each said first legacydemodulator output and said second legacy demodulator output.
 19. Themethod of claim 11 further comprising determining when the firstelectrical energy and the second electrical energy are greater than asignal threshold.
 20. The method of claim 11 further comprisingswitching to an output of said diversity demodulator when saidcorrelation value is less than said correlation threshold.